Power transmission



F. TL HARRINGTON ErAL Aug. 2 9, -1944.

POWER TRANSMISSION 1 2 Sheets-Sheet 1 Filed Oct. 12, 1938 INVENTORS FcRms T. HARRlNaToN' l. Rxnono c. cRlFrn-rH BY W .1. ATTORNE7Y- Aug. 29, Y1944.

F. T. HARRINGTON TAL PowER TRANSMISSION Filed oct; 12, 195s- 2 Sheets-Sheet 2 INVNToRs.

Frswms, T. HARRmaToN & RAYMOND C. GRIFFITH 'ATTORNEY Patented Aug. 29, 1944 POWER TRANSMISSION Ferris T. Harrington and Raymond C. Grimth,

Detroit, Mich., assigno'rs to Vickers Incorporated, Detroit, Mich., a corporation of Michigan .Application October 12, 1938, Serial N0. 234,634

9 Claims.

This invention relates to power transmissions,

particularly to those of the type comprising two or more fluid pressure energy translating devices one of 'which may function as a pump andV another as a fluid motor.

The invention is particularly concerned with a power transmission system of this character' wherein one of the energy translating devices is connected to a load device having an independent prime mover drive and wherein the power transmission may be utilized both for braking the load device and for driving the same while the prime mover is de-energized.

It is an object of the present invention to provide a control means whereby a load device may be slowed down to an adjustable slow speed and then automatically brought to a stop at a. predetermined position.

It is also an object to pro'vide'selectively operable means for operating the load device at slow speed independently of its normal drive and for stopping the load device in a predetermined position.

Further objects and advantages of the present invention will be apparent from the following description, reference being had to the accompanying drawings wherein a preferredl form of the present invention is clearly shown.

In the drawings:

Figure 1 represents a diagrammatic viewof a power transmission system incorporating a preierred form of the present invention. y

y Figure 2 represents a partially diagrammatic view of a lathe incorporating the power transmission system shown in Figure 1. y

Figures 3, 4 and 5 are diagrammatic views of the electric circuit of Figure 1 showing ythe parts in different stages of an operating cycle.

A prime mover such as an electric motor I is adapted to drive a chuck I3 on a lathe I2 through gearing I5. Operatively connected to the electric motor I0 is a fluid pressure energy translating device I4, operable at different times as a motor or a pump and hereinafter referred to as unitl4. The unit I4 may be of any suitable construction and by way of example may be constructed simi. larly to that shown in Patent fra', 1,931,969 to Hans Thoma. l

Means for the effective operation of the unit I4 are provided as follows:

A pump I6, which may be-of the xed displacement type and continuously driven by a suitable prime mover such as an electric motor I8,.has a suction conduit through which fluid may be withdrawn from` a tank 22.l The 'pump I8 delivers fluid through a relief valve and conduit 24 to a hydrostatic flow control valve 26. The latter has an adjustable throttle 21, a discharge port 28, and a pressure regulating valve 28 and is operable to maintain a constant 'but adjustable rate of flow therethrough in a manner well known inthe art. The port 28 of valve 26 is connected by a conduit 30 to a port 32 of a solenoid-operated.

spring-centered, operi-center, three-way valve 34 which has delivery ports 38 and 31.

The port 36 is connected by a conduit 38 to the unit I4. A relief valve 40 is interposed in conduit r38. A conduit 42 extends from the port 31 of valve 34 toa port. of a pressure responsive resistance valve 46. The valve 46 has a spool 48 which is normally held in its uppermost position by a spring 50, accordingly closing port 44 from a discharge port 52. A small piston 54 is subject to pressure in conduit 30 through a conduit 68. When the pressure in conduit 38 rises above the setting of the spring the piston 54 will push the spool 48 downwardly thereby connecting ports 44 and 52. The port 52 is connected, to tank 22 by a conduit v58 and a conduit 60.

The relief valve 40 has a discharge conduit 32 extending .to a check valve 84 which is connected to tank 22 by conduit 60. Connecting conduits 3U and 62 is a conduit 86 with a check valve 68 placed therein. A conduit 1I! extends from conduit 30 to the other side of unit i4. .A conduit 12 is provided to drain the unit i4, valve 34, and valve 26.

For the purpose of controlling the electric motor I0 and the `solenoids of valve 34 an electric circuit is'provided as follows:

A three-circuit push button starting switch 14 connects one side of the line L1v through its normally open lower circuit by a conductor 'I6 to the operating coil of a holding relay 18, thence/to line L2. It will be understood that L1 and L2 are connected to opposite sides of a suitable electric power supply and that, to avoid confusion in the drawing, the various parts ofthe circuit which connect to the power source are merely designated'as L1 and L2 respectively. Thezupper circuit of the relay 18 connects its operating coil to a conductor 30 which extends to the normally vclosed upper circuitof a triple-circuit push button stop switch 82 and from there to the' line L1 thus forming its ownholding circuit. The relay 1 8 is adapted to connect a circuit 84 of the electric motor I0 to power lines 85. The normally open middle circuit of switch 32 connects line L1 by la. conductor 86 to the operating -coil of a time delay relay 38, thence to line L. The upper circuit of relay 88 connects its operating coil to a conductor 80, which extends to the upper circuit of switch 14 and from there to line L1, thus forming its own holding circuit. The lower circuit of relay 88 is a snap-acting, double throw switch.

A cam 82, driven at the same speed as the chuck I3, is adapted to depress a two circuit limit switch 84 once per revolution of the chuck. A conductor 88 extends from the normally-open lower circuit of switch 82 to the operating coil of a relay 88, thence to line L2. The upper circuit of relay 88 connects its operating coil to4 a conductor |00, leading to the middle contacts of switch 14, and thence by a conductor |02 to the normally closed left hand circuit of limit switch 84, and by a parallel circuit through conductor |03 to the lower circuit of relay 88 and line L1. Thus a holding circuit, which is effective either when the cam 82 is not depressing switch 94 or when the time delay relay 88 has not shifted upwardly, is provided for relay 88. The lower circuit of relay 88 connects the line L1 to a conductor |04 which extends to a solenoid |08 of three-way valve 34, thence to line L2. The normally open right hand circuit of-limit switch 84 connects the line L1 to a conductor |08 which extends to the operating coil of a relay I I0, thence to line I?. The upper circuit of relay |I connects its operating coil to a conductor I|2 which extends to conductor 80. Thus a holding circuit for relay IIO is formed. The lower circuit of the relay ||0 extends from the line L1 through the lower circuit of relay 88 to a conductor |I4 which leads to the lower contacts of relay IIO and from there a conductor II8 extends to the two circuits of a push button switch H8. The

. normally closed upper circuit of switch I|8 extendsby a conductor |20 to a; solenoid |22 of the three-way valve 34. The normally open lower circuit of the switch |I8 extends by a conductor |24 to the conductor |04 and then to the solenoid I 08 of the valve 34.

To start the machine from its stopped condition shown in Figure 1 the push button switch 14 is momentarily depressed (as shown in Fig. 3) thereby breaking the holding circuit 90 of time delay relay 88 and the holding circuit consisting 0f` conductors 80 and ||2 of relay ,I I0. The breaking of the holding circuit for relay 88 permits the spring to operate the switch of the lower circuit thereof to open the circuit to solenoid |22 and connect the switch to conductor |03, and the circuit to the solenoid is further broken at relay IIO by breaking its holding circuit. As shown in Figure 3, accordingly the solenoid |22 is. de-energized allowing the spool of valve 34 to center itself by its centering spring. 'I'he lower circuit of switch 14 (as shown in Fig. 3) connects the line L1 to the coil of relay 18 by conductor 18 thereby energizing the same. As the relay 18 closes, the conductors 84 are connected to the power lines 88. starting the electric motor III. 'I'he holding circuit 80. which is closed at switch 82, holds the relay 18- closed to keep the electric motor I0 operating thereafter.

With the electric motor I8 running AatV` full speed and neither solenoid |88 ory |22 of valve 34 energized the unit I4 will act as a pump. Fluid will circulate with negligible resistance supercharged or under pressure by supply from pump I8 through flow control valve'f88 at a pressure determined by relief valve 25.

To stop the machine the push button switch 82 is momentarily depressed (see Fig. 4), breaking the holding circuit 80 of relay 18. Accordingly relay 18 opens and shuts off the power to the electric motor I0. Also the coil of relay 88 is energized from the line L1, switch 82, conductor 88 to the line L1. The holding circuit of relay 88 is established 4by conductor I 00, switch 14, conductor |03 and the time delay relay 88- to line L1. A branch of this circuit is also closed through conductor |02 and switch 84 to line L1. The controlled circuit of relay 88, connecting the line L1 to conductor I 04, thereby energizes solenoid |08 of valve 34 and causes the spool of .the latter to shift to the right. ,A

When the switch 82 was depressed it also made the circuit extending from line L1 by conductor 88 to the coil of time del-ay relay 88, thence'to line L1. 'I'he holding circuit of time delay relay 88 is established at once and extends from its operating coil by conductor 80 and switch 14 to connect to line L1. relay 88, however, does' not shift until a predetermined interval has elapsed, sumcient topermit the necessary deceleration of the motor I8.

When the spool of valve 34 shifted to the right.

conduit 30 was blocked at port 32 and port 88 was opened to port 31 thereby directing the delivery from unit I4 through conduit 42 to port 44 of valve 48. Due to the suction in conduits 10 and 88 caused by the unit I4 drawing more fluid than is delivered by pump I8 through conduits 80 and 10, the spool 48 of valve 48 will close and block conduit 42 at port 44. 'I'hus a back pressure is produced on unit I4 that is determined by the setting of relief valve 40. This back pressure causes the unit I4 to act as a brake for the electric motor I0. Fluid is bypassed over valve 40 and is drawn through valve 88 in conduit 88 and conduit 10 to unit I4 until the speed of the electric motor is reduced tothe point where the uid delivered from port 28 of the flow control valve 28 will again produce pressure in conduits 10 and 58. When the pressure in conduit 58 rises to the point where it will overcome from unit I4 through conduit 38, port 38 of valve' 34,` through the open-center spool of the latter to port 32 and from there by conduits 80 and 1I) the bias'of spring 50 in valve 48 the'small piston 84 will move the spool 48 downwardly, connecting port 44 to port 5 2. Conduit 38 is now con nected to tank through ports 38 and I31 of valve 34, conduit 42, ports 44 and 52 of valve 48, conduit 88 and conduit 80; Accordingly the fluid delivered by pump I8 through conduit 10 will now actuate the unit I4 as a motor to drive the electric motor at a slow rate of speed determined by the setting of the throttle 21 of valve 28.

'I'he unit I4 will thus continue to drive the electric motor at slow speed so long as the snap action of relay 88 is delayed and thereafter until the cam 82-next depresses the limit switch 84 (see Fig. 5). 'I'his opens the holding circuit of relay 88, the branch through I 03 and relay 88 having been previously opened. This opens the circuit |04. Solenoid |08 of valve 84 therefore is deenergized, which allows its spool to spring center. The switch 84 also makes a circuit extending from the line L1 and conductor |08 to the operating coil of relay IIO, thence to line L. In the meantime the controlled circuit of time delayrelay88 hasclosed and connected the line L1 by the conductor II4 to the relay IIO which is now closed. 'I'he solenoid |22 now being energized the spool of valve 34 shifts to the left.

The snap-acting switch of 'substantially instantaneously. Sufficientv rotation does occur, however, to carry the lobe of cam 92 out from under the switch 94 to its Figure 1 position. The delivery of pump li passes through now control valve 2i, conduit I0, valve 34, and conduit l42 to port 44 of valve 48. The spool of valve 4B being in its lowermost position port `44 is connected to 'port 5I. Accordingly 46, conduit 5B and conduit SII to' tank.

Although' the machine has come to a stop at a predetermined position, in response to cam 82. depressing switch 94, it may be' desirable to turther adjust the position of the lathe chuck Il. The -switch Iltis provided for this purpose and pressure fluid in conduit l! passes through valve when depressed will energize solenoid IIS to again cause unit Il-to act as a motor to drive the electric motor l0 at slow speed solong as the switch H8 is heid down.

When switch I I8 is released the solenoid iti' is deenergized and solenoid |22 becomes ener` rorfdecelerating andv braking uuid motor it.

Tae valve 25 should be set for some' intermediate pressure sumciently high to supply the torque necessary to drive fluid motor ld at the inching speed and at the same time ovefcome the bach pressure from the outlet of fluid motor it set up by the resistance cf valve di?. Valve dt, in turn, should be set at the lowest pressure of the three. The check valve 55 serves merely to create a slight back pressure in line @t during the braking phase oi' the cycle, which pressure need only be sumcient to insure opening of the check valve tti and thus prevent cavitation in line it. v

ile the form of embodiment of the inven tion as hereln'disclosed constitutes e preferred iorm. it is to be understoodthat other forms might be adopted, all coming within the scope oi. the claims which follow.

What is claimed is as follows:

i. in a fiuid power transmission system the combination of a prime mover operatively connected to a load device, a fluid pressure energy translating device operatively connected to the load device, pump means forming a. source of pressure fluid, -conduit means connecting the source and the said translating device, and valve means for controlling 'the effective paths and directions taken by the-fluid to cause the translating device at times to be driven by the prime mover and at other times to drive the prime mover by fluid suppliedfrom the source.

for causing the said device at times to be driven by the prime mover to act as a pump and at other times to act as a motor and drive the prime mover by iluid supplied from the source.

3; In a fluid power transmission system the combination of a prime mover operatively c onnected to a load device, a fluid pressure energy translating device operatively connected to the load device,- pump means forming a source of pressure fluid, conduit means connecting the source and the said translating device, and means for causing the said device selectively to be driven Y by the prime mover and act as a pump, to act as a motor and drive the prime mover by tluid supplied from the source, and, to brake the prime mover. 4. In a.v fluid power transmission system the combination of a prime mover operatively connected to a load device, a iluid pressure energy translating device .operatively connected to'the load device, pump' means forming a source of pressure fluid, conduit means connecting Ythe source and the said translating device, means forY starting the prime mover, and means to shut off the supply of power to the prime mover, means operable concurrently with'the last said means to cause the translating device to act as amotor and drive the prime mover at a predetermined slow speed by fluid delivered from the pump.

5.111 a fluid power transmission system the combination of a prime mover operatively connecteri to a load device, a duid pressure energy translating device operatively connected to the load device, pump means forming c source of pressure duid, conduit means connecting the source in driving relation to the said translating device, means for rendering the prime mover in eiiective to drive the load device, position responsive means for controlling the flow oi fluid in said conduit means to cause the load device to stop at a predetermined position, and time delay means for temporarily disabling the position re- Sponsive means.

6. in a iiuid power transmission system the combination or a prime mover operatively con..v nested to a ioad device, a fiuid pressure energy 'translating device operatively connected to the .load device, pump means forming a source of pressure uuid, conduit means connecting the source in'driving relation to the said translating device, means for starting and stopping the prime mover, means for causing the pump andl transiating device to bring the load device to a predetermined slorv speed, position responsive means for controlling the new of uuid in said conduit means to cause the load device to stop 'at a predetermined position, and means for rendering the position responsive means operative only when the load device is operating at slow speed.

'7. In a uuid power transmission system the combination of a prime mover operatively connecied to a load device, a uuid. pressure energy 2. In a uid power transmission system the combination of a prime mover operatively connected to; a load device, a Iluid pressure'energy translating device operatively connected to the load device, pump means forming asource of pressure 'i n uid; conduit' means connecting the he said translating device, andmeans only whenthe prime mover is operating at slowv speed, and manual means whereby the translating device may be operated at will at the said -slow speed.

8. In a iluid power transmission the combination of a pump, a fluid motor, a circuit connectingthe pump to the motor for operation o1' the latter, means in the circu'itfor controlling the iluid returning from the motor and responsive to a reduction in pressure'at the discharge side of the pump for blocking the normal' free return of uidf from the motor when the latter overruns the pump, and valve means shiftable to block the fluid returning from the motor independently of pressure in the pump discharge line.

9. In a. fluid power transmission the combination of a pump, a fluid motor, a circuit connecting the pump to the motor for operation of the latter, means in the circuit for controlling the of the pump for blocking the normal free return of fluid from the motor when the latteroverruns the pump, and valve means shiftable to block the iiuid returning from the motor independently of pressure in the pump discharge line, said last valve means being also shittable to open a'path from one side of the mot'or to the other to thus enable the motor to be rotated with negligible resistance.

y FERRIS T. HARRINGTON.

RAYMOND C. GRIFFITH. 

